Main bolts yielding? [Archive] - Diesel Place : Chevrolet and GMC Diesel Truck Forums

: Main bolts yielding?


oddplanes
10-19-2008, 01:59 AM
Original bolts in trash can, new GM bolts installed, threads and contact lubricated with DDA International compound #2. Have two different snap-on torque wrenches with fresh aerospace calibration (calibrated after one of the original bolts yielded) and torquing bolts to 100 outer and 110 inner, as listed in the 1994 factory manual, they don't feel right. Even had one new outer let go. is this torque a misprint?

jbsaxman
10-19-2008, 01:04 PM
What are you torquing?

jmanatee
10-19-2008, 09:53 PM
there is a difference between wet and dry torque specs... Are you sure you should lubricate the threads?

jbsaxman
10-19-2008, 10:02 PM
Didn't see that he was talking about main bolts.

Fairly sure they don't need to be lubricated.

GenBiltstein
10-20-2008, 06:32 AM
I think he is talking about main bolts on the crankshaft. I have never seen main bolts yield.
If he chimes back in and gives us an explanation..

oddplanes
10-20-2008, 11:36 AM
Main bearing cap bolts, Have the factory manual, it states to lubricate threads.

Diesel52
10-20-2008, 11:55 AM
The derating should be about 30 to 40 % for accuracy? I assume that they say to use engine oil, is there a derating factory that they recommend? ( think it should be about 30%?) If you have acces to another torque wrench try holding the bolt with the other and see if it gives at a lower setting? Move it up in incriments to see when the bolt yields? Would like to learn more on this please keep us posted?

oddplanes
10-21-2008, 01:39 PM
The bolts were stretched. so, I threw away the factory bolts and installing ARP studs. Problem solved. Still not sure why these did not torque down right. The dealer tech I talked to said he just puts them in dry.